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Introduction and Overview Image and Video Processing

Introduction and Overview Image and Video Processing. By Theerayod Wiangtong, PhD., DIC Mahanakorn University of Technology. Human Visual Perception. Eye Anatomy. Eye Vs. Camera. The Human Visual System (HVS). Human Perception of Color. Retina contains two classes of receptors:

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Introduction and Overview Image and Video Processing

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  1. Introduction and Overview Image and Video Processing By Theerayod Wiangtong, PhD., DIC Mahanakorn University of Technology

  2. Human Visual Perception

  3. Eye Anatomy

  4. Eye Vs. Camera

  5. The Human Visual System (HVS)

  6. Human Perception of Color • Retina contains two classes of receptors: • Cones (6-7 millions): • Located in the fovea • Each one connected to its own nerve end • Day vision, can perceive color tone • Red, Green, and Blue cones. • Different cones have different freq. responses • Rods (75-100 millions): • Several rods are connected to a single nerve • Night vision, perceive brightness only

  7. Range of Perception • Light consists of an electromagnetic wave with wavelength in the range 380-780 nm.

  8. Light Sources Illuminating Source Reflecting Source • Emits light (e.g. sun, bulb, TV) • Perceived color depends on spectral contents of the emitted light • Follows the additive rule: (the perceived color of several mixed illuminating light sources depends on the sum of the spectra of the light sources) • Reflects incoming light (e.g. all non-illuminating objects) • Perceived color depends on spectral contents of the reflected light • Follows the subtractive rule: (the perceived color of several mixed reflective light sources depends on the remaining (unabsorbed) wavelengths)

  9. Trichromatic color mixing theory • Trichromatic color mixing theory • Any color can be obtained by mixing three primary colors with a right proportion • Primary colors for illuminating sources: • Red, Green, Blue (RGB) • Color monitor works by exciting red, green, blue phosphors using separate electronic guns • Primary colors for reflecting sources (also known as secondary colors): • Cyan, Magenta, Yellow (CMY) • Color printer works by using cyan, magenta, yellow.

  10. Primary Colors Primary Vs Secondary Colors Secondary Colors

  11. HSV Visual Illusion

  12. HSV Visual Illusion Which lines are straight?

  13. Motion Illusion

  14. Motion Perception is Tricky

  15. Where is Human Head

  16. Test

  17. Image Processing )

  18. Digital Image Formation

  19. H=256 W=256 Matrix Representation Divide into 8x8 blocks

  20. Image Resolution

  21. Image Resolution

  22. Bitplanes Bitplane 7 Bitplane 6 Original 8bits/pixel one 8-bit byte Bitplane 7 Bitplane 5 Bitplane 4 Bitplane 0

  23. Bitplanes Bitplane 3 Bitplane 2 Original 8bits/pixel one 8-bit byte Bitplane 7 Bitplane 1 Bitplane 0 Bitplane 0

  24. Images and videos are multi-dimensional (≥ 2 dimensions) signals. Dimensionality of Digital Images

  25. Color

  26. Color Space Model YDbDr CMYK RGB L*a*b* YCrCb YIQ YUV

  27. Color: RGB Cube

  28. Conversion between RGB and YIQ in NTSC • RGB -> YIQ Y = 0.299 R + 0.587 G + 0.114 B I = 0.596 R -0.275 G -0.321 B Q = 0.212 R -0.523 G + 0.311 B • YIQ -> RGB R =1.0 Y + 0.956 I + 0.620 Q, G = 1.0 Y - 0.272 I -0.647 Q, B =1.0 Y -1.108 I + 1.700 Q.

  29. YIQ Component Y image Color Image Q image (green-purple) I image (orange-cyan)

  30. YUV in PAL

  31. Y’DbDr in SECAM

  32. Y’CbCr in Digital Image/Video Analog video Digital video

  33. Different Color TV Systems

  34. Applications Segmentation Manipulation Tracking Digital Image Processing Recognition Coding Detection

  35. Image Processing: Image Enhancement Enhance

  36. Image Processing: Image De-noising Denoise

  37. Image Processing: Image Deblurring Deblur

  38. Image Processing: Image Inpainting

  39. Image Analysis: Edge Detection

  40. Image Analysis: Face Detection

  41. Image Analysis: Image Segmentation

  42. Image Analysis: Image Matching

  43. Image Coding: Image Compression original image 262144 Bytes compressed bitstream 00111000001001101… (2428 Bytes) image encoder image decoder compression ratio (CR) = 108:1

  44. Video Processing

  45. Digital Video Processing Digital Use a digital data format Video a sequence of images along the temporal axis We will talk this more next Processing A running software program or computing operation Driven by the real-world applications (e.g., compression, filtering, retrieval)

  46. Overview of Video Processing Video Manipulation Video Display Video Compression Video Database Video Acquisition Video Transmission Computer Graphics Video Analysis Computer Vision

  47. Video Acquisition Video camera VHS digitization computer-generated

  48. Acquisition-related Problems • Video camera • What if camera is not kept still? (e.g., jittering in carphone sequence) • Why is it difficult to improve the spatial resolution of video cameras? • VHS digitization • What if VHS contains some scratches? • How to handle interlaced video? • Computer-generated • How is this type of video different? Shouldn’t we have a separate coding algorithm for this type of video?

  49. Interlaced vs Progressive scan Interlaced Progressive

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